Method and device for cooling tubes

ABSTRACT

A method and device for cooling an object, in particular a metal wire or a metal tube, is disclosed. First, the object is cooled in indirect heat exchange with a liquefied gas, then the liquefied gas is evaporated to produce a cold gas, and the cold gas is blown onto the object.

This application claims the priority of European Patent Application No. 06007311.1, filed Apr. 6, 2006, the disclosure of which is expressly incorporated by reference herein.

BACKGROUND AND SUMMARY OF THE INVENTION

The invention relates to a method for cooling an object, in particular a metal wire or a metal tube, wherein a jet of a cold gas is blown onto the object. Further, the invention is related to a device for cooling an object comprising a passageway for the object and a gas blowing device with gas outlets for directing a cold gas to the passageway.

Pending German Patent Application Number DE 10 2004 054 627 discloses a device for cooling long objects, for example tubes, by blowing cold gas onto the object. The device comprises a first chamber with a plurality of nozzles for blowing out cold gas jets. Further, an enveloping tube is provided which envelopes the object. The cold gas blown out of the first chamber flows between the object and the enveloping tube and thereby additionally cools down the object.

The device disclosed in the above-mentioned German Patent Application shows a good heat contact between the cold gas and the object. However, to enhance the heat transfer coefficient the warmed gas should be removed as fast as possible from the object to be cooled. Otherwise it will form an insulating gas buffer.

Therefore, it is an object of the present invention, to provide an improved method and an improved device for cooling an object by blowing gas jets onto it.

This object is achieved by a method for cooling an object, in particular a metal wire or a metal tube, wherein a jet of a cold gas is blown onto the object, and wherein the object is cooled in indirect heat exchange with a liquefied gas, the liquefied gas is then evaporated to produce the cold gas, and the cold gas is blown onto the object.

The inventive device for cooling an object comprises a passageway for the object and a gas blowing device with gas outlets for directing a cold gas to the passageway wherein a heat exchange passage for a liquefied gas and means for evaporating the liquefied gas in order to produce the cold gas are provided, wherein the heat exchange passage for the liquefied gas is in heat exchange contact with the passageway for the object.

According to the invention the cold of a liquefied gas is utilized to cool the object in two steps.

First, the liquefied gas is brought into indirect heat exchange with the object. The liquefied gas flows through heat exchange passages which are arranged close to the passageway where the object is placed into or passed though. By convection of the atmosphere surrounding the object heat is transferred to the liquefied gas. In addition, especially when cooling hot objects with a temperature above 500° C. there is a substantial temperature difference between the hot object and the liquefied gas. Thus, part of the heat is transferred to the liquefied gas by radiation.

Then the liquefied gas is evaporated to produce a cold gas. Part of the liquefied gas might already have been evaporated during the indirect heat exchange of the liquefied gas with the object.

Finally, the cold gas is blown onto the object to directly exchange heat with the object. By the inventive method the cold of a liquefied gas is highly efficiently utilized.

Preferably, liquid nitrogen is used as the liquefied gas.

According to a preferred embodiment of the invention, the heat exchange passages for the liquefied gas are arranged around the gas blowing device. By that arrangement the indirect cooling by the liquefied gas and the direct cooling by means of jets of cold gas is carried out at the same place. The space for cooling the object, for example the metal tube, is thus minimized.

The liquefied gas is passed through heat exchange passages to indirectly cool the object. Preferably these heat exchange passages are designed as a spiral winded around the passageway where the object to be cooled is passed through. More preferably the spiral pipeline for the liquefied gas is winded around the gas blowing device.

After having indirectly cooled the object, the liquefied gas is transferred to an evaporator where the liquefied gas is evaporated, for example, in indirect heat exchange with air or water. The resulting cold gas is fed to the gas blowing device, blown out through gas outlets, and directed to the object. Preferably the gas blowing device also comprises gas inlets arranged close to the passageway for the object. Gas which has been warmed up in heat exchange with the hot object can be withdrawn very quickly by means of these gas inlets. Thus, the heat transfer coefficient is essentially improved. It is preferred to utilize a fan or a similar device to suck in warm gas from the passageway into the gas inlets.

The invention is preferably suitable for cooling metal objects, such as tubes, wires or sheets, after a heat treatment. The inventive device can be placed in-line with the heat treatment process.

The invention as well as further details of the invention shall now be described with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an inventive device for cooling hot metal tubes.

FIG. 2 shows an alternative arrangement of the inventive gas cooling device.

FIG. 3 shows another embodiment of the gas blowing device.

DETAILED DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates the principle of the invention. The inventive method is preferably used for cooling hot metal tubes 1 after a heat treatment process when they have a temperature of approximately 1000° C.

From a storage tank 2, liquid nitrogen is transferred to a spiral pipeline 3. In the center of the spiral pipeline 3 there is a passageway where the hot tube 1 is transported through. Tube 1 is thus in indirect heat exchange with the liquid nitrogen.

There are two heat transfer mechanisms active: First, heat is transferred from the tube 1 to the spiral pipeline 3 by convection of the surrounding atmosphere. Second, due to the large temperature difference between the spiral pipeline 3 and tube 1 there is a significant heat transfer by radiation.

After leaving the spiral pipeline 3, the nitrogen partly evaporated, partly still in liquid phase, flows to an evaporator 4. In evaporator 4 the nitrogen is completely transferred into the gaseous phase. The resulting nitrogen gas is fed to a gas blowing device 5 via pipeline 6. There, the gas is distributed to several gas outlets 7 which are arranged around the passageway for tube 1. The nitrogen gas is blown out of the gas outlets 7 and directed to tube 1.

Gas outlets 7 are alternatively disposed with gas inlets 8. The nitrogen which has been warmed up by tube 1 is sucked into the gas inlets 8 and withdrawn through line 9.

FIG. 2 shows another arrangement of the gas blowing device 5 and the spiral pipeline 3. The gas blowing device 5 as well as the spiral pipeline 3 are in principle of the same design as shown in FIG. 1. However, the gas blowing device 5 is disposed within the center part of the spiral pipeline 3.

The advantage of the arrangement according to FIG. 2 is that cooling is achieved within a shorter length and that the nitrogen gas blown out of gas outlets 7 is also cooled by the liquid nitrogen flowing in spiral pipeline 3. Further, the forced flow of the nitrogen gas out of gas outlets 7 and into gas inlets 8 also enhances the convective heat transfer to the spiral pipeline 3. On the other hand, the radiative heat transfer is reduced since part of the spiral pipeline 3 is in the shape of the gas blowing device 5.

FIG. 3 illustrates another embodiment of the inventive gas blowing device especially designed for cooling of wires. For sake of simplicity, the spiral pipeline 3 is not shown in this Figure. The spiral pipeline 3 may be arranged as shown in FIG. 1 or in FIG. 2. Gas feed pipeline 6 for feeding the evaporated nitrogen gas to the gas outlets 12, 14 and pipeline 9 for withdrawing the warm nitrogen gas are also not shown in FIG. 3.

The gas blowing device comprises two wind boxes 10, 11 positioned opposite to each other on both sides of the passageway for wire 1. Both wind boxes 10, 11 comprise gas outlets 12, 14 and gas inlets 13, 15. The gas outlets 12 and the gas inlets 13 of wind box 10 are arranged alternately. The same applies for wind box 11. In addition, gas outlets 12 and gas outlets 14 of wind boxes 10 and 11 are positioned crosswise. That means, opposite gas outlet 12 of wind box 10 there is gas inlet 15 of wind box 11. Thus, the cold gas is blown out of gas outlet 12, flows around wire 1, and is sucked into gas inlet 15. And gas which is directed to wire 1 via a gas outlet 14 of wind box 11 is withdrawn through that gas inlet 13 of wind box 10 which is positioned directly opposite to gas outlet 14.

The foregoing disclosure has been set forth merely to illustrate the invention and is not intended to be limiting. Since modifications of the disclosed embodiments incorporating the spirit and substance of the invention may occur to persons skilled in the art, the invention should be construed to include everything within the scope of the appended claims and equivalents thereof. 

1. A method for cooling an object, in particular a metal wire or a metal tube, wherein a jet of a cold gas is blown onto the object, wherein the object is cooled in indirect heat exchange with a liquefied gas, the liquefied gas is then evaporated to produce the cold gas, and the cold gas is blown onto the object.
 2. The method according to claim 1, wherein liquid nitrogen is used as the liquefied gas.
 3. A device for cooling an object, comprising a passageway for the object and a gas blowing device with gas outlets for directing a cold gas to the passageway, wherein a heat exchange passage for a liquefied gas and means for evaporating the liquefied gas in order to produce the cold gas are provided, wherein the heat exchange passage for the liquefied gas is in heat exchange contact with the passageway for the object.
 4. The device according to claim 3, wherein the heat exchange passage for the liquefied gas is arranged around the gas blowing device.
 5. The device according to claim 3, wherein the heat exchange passage for the liquefied gas is designed as a spiral winded around the gas blowing device.
 6. The device according to claim 3, wherein the gas blowing device further includes gas inlets directed to the passageway.
 7. The device according to claim 6, wherein the gas inlets and the gas outlets are disposed on two opposite sides of the passageway and wherein each of the gas inlets is positioned opposite one of said gas outlets.
 8. A method of cooling an object, comprising the steps of: cooling the object with a liquefied gas; evaporating the liquefied gas after the cooling step to produce a cold gas; and blowing the cold gas onto the object.
 9. The method according to claim 8, wherein the step of cooling the object with a liquefied gas includes the step of indirectly exchanging heat from the object to the liquefied gas.
 10. The method according to claim 9, wherein the step of indirectly exchanging heat from the object to the liquefied gas includes the step of flowing the liquefied gas spirally around the object in a passage.
 11. The method according to claim 8, wherein the step of evaporating the liquefied gas is at least partially performed in an evaporator.
 12. The method according to claim 11, further comprising the step of supplying the cold gas from the evaporator to a gas blowing device, wherein the gas blowing device blows the cold gas onto the object.
 13. The method according to claim 12, further comprising the step of removing warmed cold gas from the object by the gas blowing device after the step of blowing the cold gas onto the object.
 14. The method according to claim 13, wherein the gas blowing device blows the cold gas onto the object through a gas inlet and wherein the gas blowing device removes the warmed cold gas from the object through a gas outlet.
 15. The method according to claim 14, wherein the gas inlet is disposed on a first side of the gas blowing device, wherein the gas outlet is disposed on a second side of the gas blowing device, and wherein the gas inlet is opposed to the gas outlet.
 16. A device for cooling an object, comprising: a heat exchange passage containing a liquefied gas, wherein the heat exchange passage extends around the object; an evaporator coupled to the heat exchange passage, wherein the liquefied gas is supplied from the heat exchange passage to the evaporator and wherein the evaporator transforms the liquefied gas to a cold gas; and a gas blowing device coupled to the evaporator, wherein the cold gas is supplied from the evaporator to the gas blowing device and wherein the gas blowing device blows the cold gas onto the object.
 17. The device according to claim 16, wherein the heat exchange passage spirally winds around the object and wherein the liquefied gas contained within the heat exchange passage is not in direct contact with the object.
 18. The device according to claim 16, wherein the gas blowing device includes a gas inlet and a gas outlet, wherein the gas blowing device blows the cold gas onto the object through the gas inlet, and wherein the gas blowing device removes warmed cold gas from the object through the gas outlet. 19 The device according to claim 18, wherein the gas inlet is disposed on a first side of the gas blowing device, wherein the gas outlet is disposed on a second side of the gas blowing device, and wherein the gas inlet is opposed to the gas outlet.
 20. The device according to claim 16, wherein the heat exchange passage is arranged around the gas blowing device. 